This invention relates to high strength, corrosion resistant, flexible fiber plaques, suitable for use as active material loaded electrodes in battery systems, such as nickel-cadmium, and preferably, nickel-iron battery systems.
Various types of fibrous plaques for alkaline secondary batteries have been tried in the past. One type, taught by Krebs, in U.S. Pat. No. 3,266,936, contained large numbers of clefts and protuberances due to melt connection of fibers. Such a melt connection process, while providing a strong plaque having a large fiber surface area, decreased the plaque pore volume, and thus the potential active material content. The Krebs metal fiber melt globule structure was plated with a layer of nickel, either after 800.degree. C. oxidation or after 850.degree. C. reduction sintering.
Brown et al., in U.S. Patent 3,895,960, made fiber metal plaques by diffusion bonding rather than melting the metal fibers together. After diffusion bonding, a layer of nickel was plated onto the plaque. Brown et al. taught that plating only after final diffusion bonding was essential in order to insure low electrical resistivity of the coated fiber structure. Such a structure, while providing excellent plaque pore volume, lacked somewhat in strength properties. What is needed is a metal fiber plaque structure having both high pore volume and high strength characteristics, as well as even better corrosion resistance and acceptable resistivity values.